The invention relates to a headlight for a motor vehicle.
Vehicle headlights are known, for example, from European Patent Document EP 0 900 694 A2 and from German Patent Document DE 100 40 302 A1, which conventionally have a reflector with a light source arranged at the reflector's focal point. An approximately ring-shaped optical waveguide constructed as a long rigid and stretched-out light output element, is disposed at the front edge of the reflector in the main beam radiation direction. From German Patent Document DE 100 40 302 A1, it is known to assign a second optical waveguide and a second light output element, respectively, to a neighboring vehicle headlight. The optical waveguides and light output elements are illuminated by a light source separate from the light source arranged at the reflector's focal point.
A disadvantage of these known types of headlights is that if the light source assigned to the reflector is a gas discharge lamp used, for example, as a daytime driving light, and the light source assigned to the optical waveguide is a light bulb used, for example, as a position or parking light, the color of the daytime driving light differs from the color of the position or parking light.
Another disadvantage is that due to the additional separate light source and use of the known relatively long rigid optical waveguides, the construction of the headlight assembly requires relatively high expenditures and costs and is susceptible to damage caused by the assembly.
A headlight is also known from German Patent Document DE 101 15 868 A1 that has a reflector and a light source for generating a low beam, as well as an optical waveguide element into which light from the light source is coupled out into the area of a reflector of a neighboring headlight in order to generate a further light function in the neighboring headlight. For the coupling-in of light as the light source for the optical waveguide element, an additional reflector is disposed in front of the first reflector in the main beam radiation direction that causes light emitted by the light source to be reflected essentially transversely to the main beam radiation direction of the headlight.
However, a disadvantage of this type headlight is that the surface of the additional reflector has to be relatively small in order not to form an undesirable shadowing in the light beam range of the first reflector. The limited space for construction of the additional reflector is, therefore, accompanied by a limited efficiency of the coupling of light into the optical waveguide element. A double function of two neighboring headlights can therefore virtually only be achieved by means of two active light sources.
It is therefore an object of the present invention to improve the known headlights such that, on the one hand, an additional light source is not necessary and that, on the other hand, the efficiency of the coupling of light into the optical waveguide element is increased.
These and other objects and advantages of the invention are achieved with a reflecting element being disposed in front of the light source in a main beam radiation direction in an area of the optical axis of the reflector, wherein a portion of the light of the light source, from a reflection surface of the reflecting element facing away from the main radiation direction, can be focused at a second focal point neighboring a light input surface of an optical waveguide element and therefrom is coupled into the optical waveguide element.
As a result of the reflecting element being disposed in front of the light source in an area of the optical axis, an undesirable shadowing in the edge area of the reflector, and thus in the edge area of the main beam radiation beam is avoided. By placing the reflecting element close to the center of the main radiation beam which is minimal in the reflector area, the reflecting element does not have a disturbing effect and it contributes to a desirable shadowing of unreflected rays of the light source. Thus, as a result of this favorable arrangement of the reflecting element, the forward area of the reflector remains relatively uninfluenced by the reflecting element in generating the main radiation beam, while a central rearward area of the reflector, in connection with the reflecting element, is used for coupling the light into the optical waveguide element. The need for an additional or independent light source for the optical waveguide element is thus avoided. The reflector and thus the installation space of the headlight does not have to be enlarged by the additional function and can be kept relatively flat. The construction of the vehicle headlight can furthermore be implemented relatively easily in volume in a cost-effective manner.
According to a preferred embodiment of the invention, the reflecting element is constructed as a mirror and is inclined with respect to the longitudinal axis in the main beam radiation direction such that light reflected from a first partial area of the reflector onto the mirror is directed to the light input surface of the optical waveguide element. The mirror can be constructed with a planar surface, and the mirror can be coated with a vaporized metal oxide layer in order to reduce the temperature at the optical waveguide element and at the mirror.
The planar mirror has a relatively simple and cost-effective construction and, in cooperation with the central area of the reflector adapted to it, the mirror contributes to an efficient coupling of light of the light source into the optical waveguide element.
According to another preferred embodiment of the invention, an optical waveguide is disposed in front of the reflector in a focal area of its light reflection which is forward of the reflector in the main beam radiation direction. The optical waveguide is constructed as a light output element and is placed, at least in some areas, adjacent to an edge of the reflector. The optical waveguide or the light output element has a light exit surface facing away from the reflector and a light entrance surface facing the reflector. The forward reflector area has a third focal point which coincides with the first focal point at the light source. The light of the light source is focused in this forward reflector area toward the light entrance surface of the light output element in a focal line which is adjacent to the light entrance surface of the optical waveguide. By focusing the light facing away from the light source in a focal line, the light of the light source can very efficiently be coupled into the optical waveguide. As a result, the optical waveguide can be used to generate a daytime driving light wherein the daytime driving light beam is constructed as a hollow main radiation beam.
According to another preferred embodiment of the invention, the reflector has a circular construction when viewed from the main radiation direction, and the optical waveguide is constructed as a light ring of a daytime driving light chamber bounded by the reflector.
According to another preferred embodiment of the invention, the optical waveguide element is connected with a neighboring optical waveguide of a neighboring headlight. The neighboring optical waveguide is constructed as a light output element which, at least in some of its areas, is adjacent to, or disposed in front of, an edge of a reflector of the neighboring headlight.
The neighboring optical waveguide of the neighboring headlight requires no separate light source and can radiate light in the same color as the vehicle headlight having the optical waveguide element. In this case, the neighboring optical waveguide can be constructed as a light ring of a low-beam chamber bounded by the reflector of the neighboring headlight.
According to another preferred embodiment of the invention, the optical waveguide element is fixedly connected with the neighboring optical waveguide. For example, the optical waveguide element can be molded to the neighboring optical waveguide.
The neighboring optical waveguide with the molded-on optical waveguide element can be produced and assembled in a cost-effective manner. Because of its short length, it is less susceptible to breaking. To the extent that the optical waveguide element is molded to the neighboring optical waveguide, such as by injection molding, fewer media junctions are present so that lower losses of light occur. The optical waveguides, on the whole, may have a short construction which also contributes to better luminous power.
The reflectors and optical waveguides may have a circular structure, or may have other type structures, such as a rectangular structure.
Additional details of the invention are contained in the following description and the attached drawings, in which preferred embodiments of the invention are illustrated as examples.